Known in the art is a supporting insulating column of a high-voltage accelerator, comprising sections whereto the operational potential is distributed, forming a high-potential region adjoining the high-voltage terminal of the accelerator, a low potential region thereof adjoining the grounded footing of the column and an intermediate region. The exterior surface of sections is made up of screening electrodes made as hoops with a round profile (cf., for example, U.S. Pat. No. 3,424,929 Cl. 310-5, 1969).
The round profile of electrodes results in that the electrical strength of the high potential end of the column is not high. The column is thus the weak place in the accelerator insulation and becomes the major consideration limiting the peak operating potential of the accelerator. The rupture of the column is actually the cause of the most troublesome overvoltages in the components of the accelerator whose reliability is thought of in these terms.
Also known in the art is a supporting insulating column of a high-voltage accelerator, comprising sections whereto the operational potential is distributed, forming a high potential region adjoining the high-voltage terminal of the accelerator, a low potential region adjoining the grounded footing of the column and an intermediate region, the exterior surface of said sections being composed of screening electrodes made as hoops with an oval profile oriented so that the major axis of the oval is parallel to the tangent to the exterior surface of the sections/cf., for example, Proceedings of the International Conference on the Technology of Electrostatic Accelerators, Daresbury, 1973, p. 91, 1971.
With such electrodes the increase in crosswise electrical strength is only from 10 to 15 percent and the reliability of the accelerator remains poor. The above described column uses insulating medium almost only in the high potential region, its use in other regions being insufficient.
There is also known a supporting insulating column of a high-voltage accelerator, comprising sections whereto the operating potential is distributed, forming a high potential region adjoining the high-voltage terminal of the accelerator, a low potential region adjoining the grounded footing of the column and an intermediate region, the exterior surface of said sections being composed of screening electrodes made as hoops having in at least one of the regions an oval profile oriented so that one oval vertex is facing inside the column, whereas the other vertex is directed away from the column, the major oval axis extending therethrough forms an angle with the tangent to the outside surface of sections, said angle being read from the high potential end of the column/cf., for example, Nuclear Instruments and Methods, 1980, v. 171, pp. 219-222/.
The crosswise electrical strength shows an only 10 percent increase with such electrodes. The column remains the weak link in the accelerator insulation, as compared to the high-voltage terminal. The accelerator reliability is thus hardly improved at all.
Besides, the electrical strength of the clearance between adjoining sections of this column, formed by the curved surfaces of electrodes, is not high and it becomes difficult to combine lateral and longitudinal electrical strength of the column.
Despite structural changes of electrodes in all above described columns the operational potential can be raised either by widening the gap between the column and the grounded electrode enveloping the column and the accelerator terminal or by providing additional screens in said gap/cf., for example, U.S. Pat. No. 2,230,473 Cl. 310-5, 1941/, which complicates the overall design and servicing of the accelerator, or by making use of another more expensive and stronger insulating medium.